It is proposed to investigate the immunological status of mice with mammary cancer and of mammary tumor-prone and -resistant mice of several inbred strains. Emphasis will be placed on the analysis of both cell-mediated and humoral immune response to viral and tumor antigens associated with mammary tumors as a model for immunological studies on human breast cancer. In addition, techniques and concepts developed in animal studies will be concomitantly applied to human breast cancer material in a study of antigens in cells derived from human breast cancer patients and antibodies to these antigens in the sera of these patients. Conventional immunological methods to be applied in the study include analysis of lymphocyte-mediated toxicity, blastogenesis determinations, lymphoid cell migration inhibition, cytotoxicity, immunofluorescence, immunoelectron microscopy, immunodiffusion, and radioimmunoassay. The goals of the proposed research are to determine the role of viral and tumor antigens in the immune response to breast cancer in mice and in women and to determine by these methods whether viruses similar or related to mouse mammary tumor virus may be associated with the human neoplasm.